1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an induction-type electromagnetic transducer and a method of manufacturing such a thin-film magnetic head.
2. Description of the Related Art
Thin-film magnetic heads for hard disk drives include composite type thin-film magnetic heads that have been widely used. A composite type head is made of a layered structure including a write (recording) head having an induction type electromagnetic transducer for writing and a read (reproducing) head having a magnetoresistive element (hereinafter also referred to as xe2x80x9cMR elementxe2x80x9d) for reading.
The write head has a bottom pole layer and a top pole layer each of which has a magnetic pole portion. The magnetic pole portions of the bottom and top pole layers are located on a side of the air bearing surface and opposed to each other. The write head further has a write gap layer provided between the pole portions of the bottom and top pole layers, and a thin-film coil provided such that at least a part of the coil is insulated from the bottom and top pole layers.
In recent years, to achieve higher recording density of a hard disk drive, reduction in track width of a write head in a thin-film magnetic head and increase in coercivity of a recording medium are being pursued. In association with such reduction in track width and increase in coercivity, the write head is required to generate a stronger magnetic field. Conventionally, Permalloy (NiFe) is often used as the material of a magnetic pole layer. In order to increase the intensity of the magnetic field generated by the write head, a material having a saturation flux density higher than that of Permalloy has to be used for the magnetic pole layer.
Japanese Patent Application Laid-Open Nos. 5-120630 and 6-124415 disclose a thin-film magnetic head for addressing the demand of higher recording density of a hard disk drive, in which at least one of magnetic pole layers in a write head is made up of two layers, i.e., a first layer that is not in contact with a write gap layer and a second layer that is in contact with the write gap layer. The second layer is made of a material having a saturation flux density higher than that of the material of the first layer. In the head of such a structure, decreases in the magnetic flux reaching to the tip of the pole portion on a side of a recording medium is suppressed, so that the intensity of the magnetic field generated by the write head can be increased.
On the other hand, in order to realize higher recording density of a hard disk drive, recently, it is required that the magnetic pole width of a write head be reduced to 0.5 xcexcm or less. When the magnetic pole width is so reduced, it becomes necessary to compensate decrease in the generated magnetic field in association with the reduction in the magnetic pole width. For that purpose, in a head in which the magnetic pole layer is made up of two layers as described above, the second layer having a higher saturation flux density has to be made relatively thick.
However, if the thickness of the second layer is increased, the area of a region in which the strong magnetic field is generated in a medium facing surface, that is, the area of an end portion on the medium-facing-surface side of the second layer, is increased. It increases spread of the magnetic flux on the medium facing surface. As a result, a magnetization pattern in the recording medium becomes large, and it causes problems in that it becomes difficult to improve recording density and non-linear transition shift (hereinafter referred to as NLTS) becomes large.
An object of the invention is to provide a thin-film magnetic head capable of generating a strong magnetic field from a magnetic pole portion in a medium facing surface and suppressing spread of a magnetic flux in the medium facing surface even when a magnetic pole width is small, and to provide a method of manufacturing such a thin-film magnetic head.
A thin-film magnetic head of the invention comprises: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions that are opposed to each other on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the magnetic pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. At least one of the first and second magnetic layers includes, at least in the magnetic pole portion, a first layer having surfaces one of which is adjacent to the gap layer, a second layer having surfaces one of which is adjacent to the other surface of the first layer, and a third layer having surfaces one of which is adjacent to the other surface of the second layer. The second layer has a saturation flux density higher than a saturation flux density of the third layer, and the first layer has a saturation flux density higher than the saturation flux density of the second layer.
In the thin-film magnetic head of the invention, at least one of the first and second magnetic layers includes, at least in the magnetic pole portion, the first to third layers having different saturation flux densities such that the closer the layer to the gap layer, the higher the saturation flux density. This makes it possible to suppress spread of the magnetic flux in the medium facing surface while increasing the intensity of a magnetic field generated from the magnetic pole portion in the medium facing surface.
In the thin-film magnetic head of the invention, when the thickness of the first layer in the medium facing surface is expressed as T1 and the thickness of the second layer in the medium facing surface is expressed as T2, the value of T1/(T1+T2) may be in a range from not less than 0.025 to not more than 0.5. The value of T1/(T1+T2) may be also in a range from not less than 0.05 to not more than 0.25.
In the thin-film magnetic head of the invention, when the saturation flux density of the first layer is expressed as B1 and the saturation flux density of the second layer is expressed as B2, the value of B2/B1 may be in a range from not less than 0.65 to not more than 0.95. The value of B2/B1 may be also in a range from not less than 0.75 to not more than 0.95.
According to the invention, there is provided a method of manufacturing a thin-film magnetic head comprising: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions that are opposed to each other on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the magnetic pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. The method comprises the steps of: forming the first magnetic layer; forming the gap layer on the first magnetic layer; forming the second magnetic layer on the gap layer; and forming the thin-film coil. At least one of the steps of forming the first magnetic layer and forming the second magnetic layer forms, at least in the magnetic pole portion, a first layer having surfaces one of which is adjacent to the gap layer, a second layer having surfaces one of which is adjacent to the other surface of the first layer, and a third layer having surfaces one of which is adjacent to the other surface of the second layer. The second layer has a saturation flux density higher than a saturation flux density of the third layer, and the first layer has a saturation flux density higher than the saturation flux density of the second layer.
In the method of manufacturing a thin-film magnetic head of the invention, at least one of the first and second magnetic layers includes, at least in the magnetic pole portion, the first to third layers having different saturation flux densities such that the closer the layer to the gap layer is, the higher the saturation flux density is. This makes it possible to suppress spread of the magnetic flux in the medium facing surface while increasing the intensity of a magnetic field generated from the magnetic pole portion in the medium facing surface.
In the method of manufacturing a thin-film magnetic head of the invention, when the thickness of the first layer in the medium facing surface is expressed as T1and the thickness of the second layer in the medium facing surface is expressed as T2, the value of T1/(T1+T2) may be in a range from not less than 0.025 to not more than 0.5. The value of T1/(T1+T2) may be also in a range from not less than 0.05 to not more than 0.25.
In the method of manufacturing a thin-film magnetic head of the invention, when the saturation flux density of the first layer is expressed as B1 and the saturation flux density of the second layer is expressed as B2, the value of B2/B1 may be in a range from not less than 0.65 to not more than 0.95. The value of B2/B1 may be also in a range from not less than 0.75 to not more than 0.95.
Other and further objects, features and advantages of the invention will appear fully from the following description.